Transport studies of dual-gated ABC and ABA trilayer graphene: band gap opening and band structure tuning in very large perpendicular electric field

TL;DR

This study investigates how applying large perpendicular electric fields affects the electronic properties of ABC and ABA trilayer graphene, revealing a significant band gap in ABC but not in ABA, with detailed experimental and theoretical analysis.

Contribution

It provides the first detailed transport measurements of dual-gated ABC and ABA trilayer graphene under large electric fields, demonstrating band gap opening in ABC trilayer and ongoing band structure evolution in ABA.

Findings

ABC trilayer exhibits a six-order magnitude resistance change indicating a band gap.

The band gap in ABC saturates at a displacement field of ~3 V/nm.

ABA trilayer remains metallic but shows band structure changes and two-band conduction signatures.

Abstract

We report on the transport properties of ABC and ABA stacked trilayer graphene using dual, locally gated field effect devices. The high efficiency and large breakdown voltage of the HfO2 top and bottom gates enables independent tuning of the perpendicular electric field and the Fermi level over an unprecedentedly large range. We observe a resistance change of six orders of magnitude in the ABC trilayer, which demonstrates the opening of a band gap. Our data suggest that the gap saturates at a large displacement field of D ~ 3 V/nm, in agreement with self-consistent Hartree calculations. In contrast, the ABA trilayer remains metallic even under a large perpendicular electric field. Despite the absence of a band gap, the band structure of the ABA trilayer continues to evolve with increasing D. We observe signatures of two-band conduction at large D fields. Our self-consistent Hartree calculation reproduces many aspects of the experimental data, but also points to the need for more sophisticated theory.